The present invention relates to door security hardware and, more particularly, to a door latch guard for guarding the latch of an outwardly opening door.
Conventional door locking mechanisms typically utilize a retractable spring-loaded latch operated by a door knob rotatable from either side of the door. When the door is closed, the latch contacts a latch strike plate causing the latch to recede within the door until it is aligned with a socket formed within the door jamb or frame. Once aligned, the latch springs into the socket to retain the door in the closed position. The door knob typically has a button-type locking mechanism on one side which can be actuated to prevent the knob from being rotated to retract and disengage the latch from the socket. The opposite side of the door knob typically has a key mechanism for disengaging the locking mechanism so that the knob can be rotated to retract the latch from the socket and open the door.
Knob-type door locks of the type described above often can be violated by techniques commonly used by unwanted intruders. For example, many latches can be disengaged from the socket by simply sliding a flexible strip of material, such as a plastic credit card, between the door and the door frame, thereby allowing the door to be opened even though the door knob is incapable of being rotated. Other tampering techniques include inserting rigid objects, such as jimmy bars or screwdrivers, between the door and the door frame to pry the latch from the socket. The door latch also can be disengaged from the socket by spreading the vertical frames of the door at the level near the latch. In order to spread the frame, intruders commonly use a car-jack type device positioned horizontally between the vertical frames of the door at the level of the latch. When the jack is cranked, it spreads the vertical frames such that the latch becomes partially or totally removed from the socket, allowing the door to be opened or easily kicked open by the intruder.
To avoid the problems associated with most knob-type locking mechanisms described above, the owners of commercial and residential buildings often install a dead bolt lock in the door, in addition to the knob-type lock. Unfortunately, although dead bolt locks are less susceptible to being violated by plastic credit cards and the like, they are not totally resistant to forced methods of entry involving spreading of the vertical frames around the latch to facilitate kick-in attacks.
To further combat the above-identified problems, so-called latch guards have been developed. A typical latch guard comprises an elongated cover plate connected to the door and having a portion adapted to overlie the adjacent door frame. To accommodate the latch strike plate extending outwardly from the door frame, the cover plate has an elongated V-shaped groove to provide a space on the inside surface of the cover plate for receiving the protruding latch strike plate. These latch guards also include an anti-spread pin in the portion of the cover plate that overlies the adjacent door frame. The anti-spread pin typically has a shaft adapted to extend into a hole in the door frame to limit spreading of the frames by an intruder using the methods described above.
While latch guards of the type described above generally have been effective for preventing tampering with the latch and spreading of the door frames, they have been plagued by installation problems and other undesirable drawbacks. For example, most residential locks are installed at a certain distance from the edge of the door called the backset. Residential locks typically are installed at a backset of approximately 23/8 inches, while commercial locks are typically installed at a backset of approximately 23/4 inches. When the V-shaped groove of the cover plate is properly positioned to accept the protruding latch strike plate, oftentimes the cover plate will overlie a portion of the lock hardware on the outside surface of the door. Accordingly, the installer must carve out a portion of the cover plate to accommodate the lock hardware so that the cover plate can be installed flat against the door.
These carving procedures, however, are a very time consuming and undesirable operation. This is true even when only a single lock is installed on the door, such as a knob-type lock. Moreover, if both a knob-type lock and a dead bolt-type lock are used, the time and trouble in making two separate cutouts in the cover plate is doubled. Carving of the cover plate generally cannot be avoided, since the failure to carve the cover plate to accommodate the lock hardware will cause the V-shaped groove to be misaligned with the protruding latch strike plate, such that the groove will contact the latch strike plate, rather than freely receive it, thus preventing proper installation of the cover plate flat against the door. Even in cases where the cover plate is pre-carved to accommodate the lock hardware, it usually is not carved to receive both a knob-type lock and a dead bolt-type lock. Such pre-carved plates also are not carved sufficiently to accommodate locks installed at different backsets, nor are they adapted for use with mortise locks or locks having large escutcheons.
In addition, bolts generally are used to install the latch guard on the door. These bolts typically have an enlarged head adapted to engage the outer surface of the cover plate, and an externally threaded shaft extending through a mounting hole in the cover plate and through a hole in the door. An internally threaded retaining nut, such as an acorn nut, is used to secure the shaft of each bolt at the back side of the door. In some prior art latch guards, however, the mounting holes in the cover plate are in such a position that, when the retaining nuts are installed on the bolt shaft at the back side of the door, the nuts interfere with a door stop on the door frame that keeps the door from swinging inwardly during closing of the door. In such cases, the installer must carve out a portion of the door stop to receive the protruding nuts. This procedure is made especially difficult when steel door frames and door stops are used. Oftentimes, the door frame and door stop are filled with concrete for reinforcing purposes. Hence, the installer must use two drill bits, one for drilling through the steel door stop and one for drilling through the concrete behind it, to carve out sufficient space to accommodate the retaining nuts. This causes further inconvenience for the installer.
Accordingly, there has existed a definite need for a latch guard for outwardly opening doors that protects the latches on doors having multiple locks positioned one above the other, that accommodates the protruding latch plates for locks installed at different backsets, and which does not require any special drilling or carving operations to install the latch guard. The present invention satisfies these needs and provides further related advantages.